The present invention relates generally to new and novel improvements in time-dependent data control systems. More particularly, the present invention relates to data control systems which allow data to be transmitted from a control unit to a plurality of individual terminals such that each individual terminal can begin using the data thus transmitted independently of the other terminals either at a single preset time or at a predetermined number of preset times.
In many conventional data control systems, data is transmitted from a control unit to a plurality of terminals and the individual terminals begin using the information transmitted from the control unit immediately upon receipt of the data. However, in these conventional systems, unless relatively expensive high speed data communication equipment is used or the number of individual terminals is small, differences in the data receiving time among individual terminals can be significant. Hence, the time at which the processing is started in accordance with the changed data can significantly differ among the different terminals.
Such variations in the time the terminals begin using the transmitted changed data as described above is undesirable in many data processing applications. For example, in the case of a merchandise article price display system or the like such as that used in supermarkets and other large retail stores, the possibility exists that the same merchandise articles could have different prices displayed at the same time at different display locations within the store if multiple price displays are used. The purpose of such a merchandise article price display system is to inform customers of current price information. Therefore, erroneous displays of the current price can cause customer confusion and ill will. Furthermore, since in typical merchandise article price display systems used in supermarkets and large retail stores many individual price displays are utilized, it is often undesirable to utilize high speed data communication equipment due to its complexity and cost.
A representative calculation of the communication time needed for changing price information in such conventional price display systems will now be described. Assuming that the number of price displays installed is 1,000, the data communication speed is 1,200 bits per second (BPS) with an execution efficiency of 70% and that the data length is 40 bytes, it will take eight minutes from the start of data transmission to the individual price displays until the last price display is changed. This means that price displays for the same merchandise articles can display different price information for up to eight minutes. It will be recognized that this time delay will increase as the number of individual price displays is increased, and supermarkets and other large retail stores often utilize 20,000 or more individual price displays.
Accordingly, an object of the present invention is to provide a time-dependent data control system where data is transmitted from a control unit to a plurality of terminals and each individual terminal can begin utilizing the data transmitted at a predetermined time after the transmission of data has occurred.
Another object of the present invention is to provide a time-dependent data control system where data is transmitted from a control unit to a plurality of terminals and each of the plurality of terminals can begin utilizing the data transmitted simultaneously at a predetermined time after the transmission of data has occurred.
A further object of the present invention is to provide a time-dependent data control system having a control unit and a plurality of terminals with clock means such that the times of the clock means of all of the individual terminals can be set upon reception of the data from the control unit.
Yet another object of the present invention is to provide a time-dependent data control system having a control unit and a plurality of terminals with clock means and the terminals are adapted to automatically change the displayed data in the individual terminals to the transmitted changed data at a preset change time.
Still a further object of the present invention is to provide a time-dependent data control system having a control unit and a plurality of terminals in which the energy requirements and power consumption of the individual terminals are minimized.
These and other objects of the present invention are attained by the provision of a time-dependent data control system having a control unit and a plurality of price display terminals where changed data and change time are transmitted from the control unit to each price display terminal prior to the time at which the individual price display terminal is to utilize the changed data. Once the data is transmitted from the control unit to each price display terminal, the price display terminal compares the current time with the change time by clock means installed within the price display terminal. The individual price display terminal will then utilize the transmitted changed data to change the price display when the change time has come.
The control unit also includes provisions such that when the change time is transmitted to each price display terminal, the time data in a clock means installed in the control unit is transmitted to the price display terminals as a reference time. This permits each price display terminal to set the time in its internal clock means to the reference time transmitted from the control unit. Thus, the clock means of each price display terminal is periodically adjusted to correspond with the reference time present in the control unit clock means.
When transmission of data from the control unit to the price display terminals is to be started, a start of transmission signal of a given length is transmitted to each price display terminal in such a manner that each price display terminal will switch from a standby rest mode into an enable period. This minimizes the energy requirements and power consumption of the individual price display terminals.
Other objects, advantages and novel features of the present invention will become apparent in the following detailed description of the invention when considered in conjunction with the accompanying drawings.